Field of the Invention
Embodiments of the present invention relate generally to semiconductor substrate processing and, more particularly, to plasma processing in a plasma processing chamber having one or more radio frequency power feeds for improved process uniformity.
Description of the Related Art
Plasma processing, such as plasma-enhanced chemical vapor deposition (PECVD), is generally employed to deposit thin films on substrates, such as semiconductor substrates, solar panel substrates and liquid crystal display (LCD) substrates. Uniformity of such thin films, both in thickness and quality, is generally desired and, as substrates increase in size, is increasingly difficult to attain. In fact, as the size of semiconductor devices formed with these films continues to decrease, the requirements for thickness uniformity and other film properties often become even more stringent.
Asymmetries inherent in the configuration of many chemical vapor deposition reactors can further compound difficulties in achieving thin film uniformity. For example, for many PECVD chambers used to process semiconductor substrates (e.g., 300 mm diameter substrates), the layout is generally configured to be cylindrically symmetrical to facilitate a cylindrically symmetrical electric field in the chamber during processing. However, the presence of a slit valve formed in one wall of the chamber for insertion and removal of substrates necessarily disrupts this symmetry and can result in film thickness skew that varies from one side of the chamber to an opposite side of the chamber. In addition, connection of the radio-frequency power feed at a center point of a PECVD chamber discharge electrode, while conducive to producing a radially uniform electric field, can be inaccessible due to the presence of other external chamber components that prevent the connection at the center point of the electrode. Thus, a radio-frequency power feed for some PECVD chambers may be positioned on the discharge electrode at some point besides the geometric center, which is generally suboptimal with respect to generating a radially symmetric electric field in the chamber. Non-symmetric electric fields will generally cause a plasma generated in the processing region of a processing chamber to be non-uniform, which will cause the deposition or etching process performed in the processing chamber to be non-uniform.
Accordingly, there is a need in the art for systems and methods that facilitate improved uniformity of an etching process or a thin film deposition process performed in a plasma processing chamber.